JPS60169578A - Method for preventing corrosion and contamination of shell plate - Google Patents

Abstract

PURPOSE:To prevent semipermanently corrosion and contamination by covering the shell plate by covering said plate with a copper-base metallic material and maintaining the protective current value only during sailing at an optimum value based on specific potential thereby effecting electrolytic corrosion. CONSTITUTION:The submerged part of a shell plate is covered by a copper or copper alloy material 2. A power source 3 in the ship and an electrode 4 which is hoisted up and down by a hoisting device 6 are connected by a conductor 5 and the material 2 and the power source 3 as well as one end of a control device 8 are connected by a conductor 7. The device 8 detects the sailing and stop of the ship, commands the device 6, is inputted with the potential difference between the electrode 4 and the material 2, i.e., the voltage between the branch conductor 11 of the conductor 5 and the conductor 7 and detects the corrosion preventing condition of the material 2. The power source 3 turns off and the device 6 lifts the electrode 4 from the sea when the ship calls at a port. Then the material 2 elutes to generate an effect of preventing contamination. When the ship leaves the port, the device 6 casts the electrode 4 into the sea by the command from the device 8 and the power source 3 is turned on by the signal passing through the wire 10 of the device 8 then protective current 13 flows from the electrode 4 into the material 2, thereby decreasing the elution of the copper. The device 8 controls the power source 3 by applying the signal operating the potential of the material 2 via the conductor 10 to said power source by the above-mentioned input.

Description

[Detailed description of the invention] It is something.

Conventional anti-corrosion and anti-fouling methods for ship hulls (preventing marine organisms such as slime from getting onto the outer panels of the hull) involve applying anti-corrosion paint to the outer panels (usually made of steel). This is achieved by cathodic protection, which is a primer coat and then a top coat of antifouling paint. The antifouling paint contains, for example, D metals such as cuprous oxide or organic tin, and achieves the purpose of antifouling by gradually eluting these metals.

On the other hand, in order to prevent corrosion of the outer panel caused by scratches on the paint film caused by driftwood, etc., the corrosion protection current can be removed by using metals that are more base than the outer panel, such as zinc or aluminum alloys, or by the electromotive force of an external power source. It flows into the plate to achieve the purpose of corrosion prevention.

The disadvantages of this antifouling and anticorrosion synutem are that it is necessary to dock the ship every 1 to 2 years and reapply the antifouling paint, and as the antifouling and paint elutes, the surface of the ship becomes rougher. This increases the hull resistance.

In response, it has been proposed to make hull shells from copper or copper alloy clad steel, which has corrosion resistance and antifouling properties. But for this.

If the copper cladding material is damaged due to an unexpected accident, the underlying steel will be severely corroded due to electrolytic corrosion with the copper cladding material. Therefore, in order to prevent abnormal wear and tear on the steel parts, measures such as inserting an insulating phase between the steel and the antifouling metal steel or copper alloy have been taken.

Furthermore, in the case of elution of effective antifouling metals from such surfaces, it is necessary to consider the following secondary matters.

(1) For antifouling to be effective, the concentration of effective metal ions on the surface must be maintained at a certain value or higher. (Metal elution rate must exceed a certain value.) Ion concentration must not change over time.

(2) Biological attachment (activity) is active in still seawater.

In flowing seawater, the number of clothes is less than 1 inch or not at all.

(3) Effective metal ions from antifouling paints and antifouling metals are often eluted in flowing seawater.

m, (2+, (3)) means that living things are present when the ship is at anchor.
On the other hand, the elution of effective metal ions must be less when anchored and more when cruising.

In other words, the antifouling metal plate is wasted and consumed during navigation.
This means that thick antifouling metal plates must be used frequently on ocean-going ships that spend a long time at sea.

On the other hand, if you use an antifouling metal plate that has sufficient corrosion resistance even in fast-flowing seawater like when sailing.

As a result of insufficient bathing speed when berthed, a contradiction arises in that the antifouling effect is insufficient. Furthermore, it is essential for the antifouling metal plate to dissolve uniformly over the entire surface in order to reduce hull resistance during navigation.

In the present invention, instead of the conventional antifouling paint, the outer panel of the hull is covered with a metal material such as copper or copper alloy to which living organisms do not adhere, and cathodic protection is applied only when the ship is sailing.

In addition to providing a semi-permanent anti-corrosion and anti-fouling method, electrodes are dropped into the sea only during navigation, and the value of the anti-corrosion current flowing from the electrode to the base copper or copper alloy material is determined between the electrode and the steel. According to the present invention of the hull shell plate, which is characterized in that the voltage between the copper alloy materials and the potential of the electrode is maintained at an optimum value by the onboard power supply, the steel hull shell plate is (Able to reduce the wear and tear of copper or copper alloy materials coated with 2) and to prevent the formation of a corrosion-resistant protective film on the surface.
If the vessel is stopped for an hour or so, it is possible to prevent marine organisms from adhering to the outer shell of the vessel.

Below 1. An embodiment of the present invention will be described in detail based on FIG.

In FIG. 1, reference numeral 91 denotes a steel hull shell plate, and 2 denotes a copper alloy material that covers the submerged portion of the outer plate 1.

3 is a DC power supply installed inside the ship, and 4 is an electrode dropped into the tIU.

Now, cathodic protection is generally well known as a method for controlling corrosion of metals in seawater.

For ships, an external power automatic corrosion protection method has been put into practical use, in which a reference electrode is attached to a part of the outer shell to serve as a potential reference, and a direct current is passed from the onboard power supply to the outer shell metal so that the potential of the outer shell metal exhibits a constant value. has been done. However, when this method is applied to the present invention, a part of the copper or copper alloy material covering the hull shell is peeled off, and a reference electrode made of a material other than steel or copper alloy is brought into contact with seawater. In order to be able to take it as it is,
The drawback is that marine life grows from this area.

The present invention has been developed with this point in particular in mind.

Hereinafter, embodiments of the present invention will be described in detail based on FIG.

In FIG. 1, reference numeral 1 denotes a steel hull outer plate, and 2 a copper or copper alloy material that covers the submerged portion of the outer plate 1.

3 is a DC power supply installed in the ship; 4 is an electrode dropped into the sea; 5 is a conductor connecting the power supply 3 and the electrode 4; 6 is a lifting device for hoisting and lowering the i-1 conductor 5 and the electrode 4; 7 is a conductive wire connecting the steel or copper alloy material 2 to the power source 3 and the L end of the control device 8, which detects whether the 8-boat boat is running or stopped and at the same time commands hoisting and lowering of the electrode 4; 9 is a control device that has the function of detecting the corrosion protection state of the steel heavy copper alloy material 2 and supplying current to the electrode 4 from the power source 3 through all the conductors 5, and commanding the flow value; 6 and the control device 8, and 10 is a conducting wire for transmitting a current value command signal from the control device 8 to the power source 3.

If the hull outer plate 1 and the copper 1 tuning alloy (32) are electrically connected (C is conductor fL1g7 may be connected to the hull outer plate 1).

In addition, in order to detect the corrosion protection state of the copper alloy material 2, the potential difference between the electrode 4 and the copper or copper alloy 122, that is, the voltage between the conductor j1 branched from the bright line 5 and the conductor 7, is determined. All you have to do is input it to the control device 8. Then, based on this human input signal, an output signal for controlling the potential of the copper alloy material 2 by flt+-4 is given to the electric wire 3 via the core wire 10 for control. This principle will be described later with reference to FIG.

When a ship having the structure described above visits a port, the power supply 3 is turned off, the lifting device 6 is operated to wind up the conductor 5, and the electrode 4 is pulled out of the sea and stored on the ship. As a result, the copper or copper alloy material 2 is left in a natural state in seawater, corrosion begins, and the main component copper is eluted from the surface 9, and CuCARr ions cover the submerged parts of the ship's hull and have an antifouling effect. arise.

When the ship leaves the port, the lifting device 6 is activated according to a command from the control device 8, and the electrode 4 is dropped into the sea.At the same time, a signal from the control device 8 is transmitted to the power source 3 through the conductor 10, and the power source 3
is turned on, the anti-corrosion current 13 flows from the electrode 4 into the copper or copper alloy material 2, the copper leakage is reduced by the cathodic protection action, and the formation of a strong anti-corrosion protective film on the surface is prevented.

Generally, the current l required for this corrosion protection is expressed by the following equation.

f(S, V, T, t, o, M...)...
・・・・・・・・・・・・(1) Here, S: Hull area, V: Ship speed, T: Seawater temperature, t: Time, 0: Seawater quality 1
M: Type of metal These complicated factors can be easily controlled by means described below.

Since passing current consumes energy, it is important to uniformly distribute the current to each part of the ship and lower the voltage.
This is important from the perspective of energy conservation. This/Kome No. 1
The four towed chambers shown in the figure, which allow current to flow from the ship's tag, are extremely effective in making the current distribution uniform. Sometimes, on large ships bound for the open ocean, the method of attaching several electrodes to the outer skin of a hull is difficult to put into practical use because it is necessary to penetrate a large number of electrodes through the outer skin of the hull. In terms of quality and personnel requirements during energization, it is preferable to use insoluble electrodes such as plated or burnt copper alloy 1'4±VC white metal such as titanium or tantalum.

Now, why is it possible to maintain the potential of the copper or copper alloy material 2 at a desired potential by inputting the voltage between the copper alloy material 2 and the electrode 4 to the control device 8? will be explained in detail with reference to Fig. 2.Two metals a and C exist in a uniform conductive medium W9, for example, seawater, as shown in Fig. 2, and a voltage E is applied from a power supply having an internal resistance Jii. is given and a current I flows.If the polarization voltage of metals a and c is ε8.ε, then this is a.

The voltage between 0 and ■1 has the following relationship.

V B c-E I Rj-(E a1εa) (Ec
1εc) - IR8 (2) Here, Ea is the natural potential of metal a, EC is the natural potential of metal C, R51da+
Shows the ring resistance and liquid resistance between c.

From formula (2), (EC1εC)2Vac (Ea+εa) + I
RS ・=・−−−−(3) Equation (3) is the cathode potential (
EC+εC)'fg: Instead of measuring the voltage Vac between the conductors 11 and 7 in Figure 1 +/C, the anode box of the flashlight 4, the position (E, +68), the loss due to wire resistance and liquid resistance. This shows that the same result can be obtained even if each term on the right side of the voltage IR8 is studied.

As explained above, the effects of the present invention are as follows. By suppressing the wear and tear of the antifouling metal plate during navigation, the life of the antifouling metal plate can be made extremely long; 1) Expensive materials can be made thinner, making it more economical to use; Since anti-fouling materials were selected based on the overall durability during running, it is now possible to select anti-fouling materials with a large amount of corrosion that have sufficient anti-fouling effects, even though they tended to have insufficient anti-fouling effects when moored. That's true. Furthermore, if the copper hull skin 1 and the steel or copper alloy material 2 are in direct contact, the copper or copper alloy material 2 may be damaged for some reason during navigation, causing the skin 1 to come into direct contact with seawater. Even in such a case, the present invention can prevent the progress of corrosion. It goes without saying that according to the present invention, corrosion of the copper or copper alloy material 2 can be prevented even when an insulating layer is provided between the outer plate 1 and the copper or copper alloy material 2.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the principle of the present invention. 1... Hull outer plate, 2... Button or copper alloy lever, 3.
...power supply, 4...electrode, 6...lifting device, 8...
Control device. 5.7, 9, 10.11... Conductor wire, 13... Corrosion protection current, W... Conductive medium, a, c... Metal. Agent Kneeling for 1 minute;・j] 4 Riharude

Claims (1)

[Claims] The steel hull outer plate is fully coated with copper or copper alloy jl:A, and electrodes are dropped into the sea only during navigation. The anticorrosion current value flowing from the noble electrode to the base copper or copper alloy material is maintained at an optimum value by an onboard power source based on the voltage between the electrode and the copper or copper alloy phase and the potential of the electrode. Anti-corrosion and antifouling method for hull outer plating.